On 03/14/2017 10:12 AM, Richard Biener wrote:
> On Tue, 14 Mar 2017, Martin Liška wrote:
>
>> On 03/14/2017 09:13 AM, Richard Biener wrote:
>>> On Tue, 14 Mar 2017, Martin Liška wrote:
>>>
>>>> On 03/13/2017 04:16 PM, Richard Biener wrote:
>>>>> On Mon, 13 Mar 2017, Martin Liška wrote:
>>>>>
>>>>>> On 03/13/2017 02:53 PM, Richard Biener wrote:
>>>>>>> On Mon, 13 Mar 2017, Martin Liška wrote:
>>>>>>>
>>>>>>>> On 03/13/2017 02:01 PM, Richard Biener wrote:
>>>>>>>>> On Mon, 13 Mar 2017, Richard Biener wrote:
>>>>>>>>>
>>>>>>>>>> On Fri, 10 Mar 2017, Martin Liška wrote:
>>>>>>>>>>
>>>>>>>>>>> Hello.
>>>>>>>>>>>
>>>>>>>>>>> As briefly discussed in the PR, there are BB that do not correspond
>>>>>>>>>>> to a real
>>>>>>>>>>> line in source
>>>>>>>>>>> code. profile.c emits locations for all BBs that have a gimple
>>>>>>>>>>> statement
>>>>>>>>>>> belonging to a line.
>>>>>>>>>>> I hope these should be marked in gcov utility and not added in
>>>>>>>>>>> --all-block
>>>>>>>>>>> mode to counts of lines.
>>>>>>>>>>>
>>>>>>>>>>> Patch survives make check RUNTESTFLAGS="gcov.exp".
>>>>>>>>>>>
>>>>>>>>>>> Thanks for review and feedback.
>>>>>>>>>>
>>>>>>>>>> Humm, the patch doesn't seem to change the BBs associated with a line
>>>>>>>>>> but rather somehow changes how we compute counts (the patch lacks a
>>>>>>>>>> description of how you arrived at it). I expected the line-to-BB
>>>>>>>>>> assignment process to be changed (whereever that is...).
>>>>>>>>
>>>>>>>> Currently, each basic block must belong to a source line. It's how gcov
>>>>>>>> iterates all blocks (via lines).
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Ah, ok, looking at where output_location is called on I see we do not
>>>>>>>>> assign any line to that block. But still why does
>>>>>>>>> line->has_block (arc->src) return true?
>>>>>>>>
>>>>>>>> Good objection! Problematic that 4->5 edge really comes from the same
>>>>>>>> line.
>>>>>>>>
>>>>>>>> <bb 4> [0.00%]:
>>>>>>>> ret_7 = 111;
>>>>>>>> PROF_edge_counter_10 = __gcov0.UuT[0];
>>>>>>>> PROF_edge_counter_11 = PROF_edge_counter_10 + 1;
>>>>>>>> __gcov0.UuT[0] = PROF_edge_counter_11;
>>>>>>>>
>>>>>>>> <bb 5> [0.00%]:
>>>>>>>> # ret_1 = PHI <ret_5(3), ret_7(4)>
>>>>>>>> goto <bb 7>; [0.00%]
>>>>>>>
>>>>>>> Yes, but that's basically meaningless, unless not all edges come from
>>>>>>> the
>>>>>>> same line? I see nowhere where we'd explicitely assign lines to
>>>>>>> edges so it must be gcov "reconstructing" this somewhere.
>>>>>>
>>>>>> That's why I added the another flag. We stream locations for basic
>>>>>> blocks via
>>>>>> 'output_location' function. And assignment blocks to lines happens here:
>>>>>>
>>>>>> static void
>>>>>> add_line_counts (coverage_t *coverage, function_t *fn)
>>>>>> {
>>>>>> ...
>>>>>> if (!ix || ix + 1 == fn->num_blocks)
>>>>>> /* Entry or exit block */;
>>>>>> else if (flag_all_blocks)
>>>>>> {
>>>>>> line_t *block_line = line;
>>>>>>
>>>>>> if (!block_line)
>>>>>> block_line = &sources[fn->src].lines[fn->line];
>>>>>>
>>>>>> block->chain = block_line->u.blocks;
>>>>>> block_line->u.blocks = block;
>>>>>> }
>>>>>>
>>>>>> where line is always changes when we reach a BB that has a source line
>>>>>> assigned. Thus it's changed
>>>>>> for BB 4 and that's why BB 5 is added to same line.
>>>>>
>>>>> Ah, so this means we should "clear" the current line for BB 5 in
>>>>> output_location? At least I don't see how your patch may not regress
>>>>> some cases where the line wasn't output as an optimization?
>>>>
>>>> The new flag on block is kind of clearing that the BB is artificial and in
>>>> fact does not
>>>> belong to the line. I didn't want to do a bigger refactoring how blocks
>>>> are iterated via lines.
>>>>
>>>> Can you be please more specific about such a case?
>>>
>>> in profile.c I see
>>>
>>> if (name_differs || line_differs)
>>> {
>>> if (!*offset)
>>> {
>>> *offset = gcov_write_tag (GCOV_TAG_LINES);
>>> gcov_write_unsigned (bb->index);
>>> name_differs = line_differs=true;
>>> }
>>>
>>> ...
>>>
>>> so if line_differs is false we might not output GCOV_TAG_LINES either
>>> because 1) optimization, less stuff output, 2) the block has no line.
>>> Looks like we can't really distinguish those.
>>
>> Agree with that.
>>
>>>
>>> Not sure how on the input side we end up associating a BB with
>>> a line if nothing was output for it though.
>>>
>>> That is, with your change don't we need
>>>
>>> Index: gcc/profile.c
>>> ===================================================================
>>> --- gcc/profile.c (revision 246082)
>>> +++ gcc/profile.c (working copy)
>>> @@ -941,8 +941,6 @@ output_location (char const *file_name,
>>> name_differs = !prev_file_name || filename_cmp (file_name,
>>> prev_file_name);
>>> line_differs = prev_line != line;
>>>
>>> - if (name_differs || line_differs)
>>> - {
>>> if (!*offset)
>>> {
>>> *offset = gcov_write_tag (GCOV_TAG_LINES);
>>> @@ -950,6 +948,9 @@ output_location (char const *file_name,
>>> name_differs = line_differs=true;
>>> }
>>>
>>> + if (name_differs || line_differs)
>>> + {
>>> +
>>> /* If this is a new source file, then output the
>>> file's name to the .bb file. */
>>> if (name_differs)
>>>
>>> to resolve this ambiguity? That is, _always_ emit GCOV_TAG_LINES
>>> for a BB? So then a BB w/o GCOV_TAG_LINES does _not_ have any
>>> lines associated.
>>
>> That should revolve it. Let me find and example where we do not emit
>> GCOV_TAG_LINES jsut because there's not difference in lines.
>
> sth like
>
> a = b < 1 ? (c < 3 ? d : c);
>
> or even
>
> if (..) { ... } else { ... }
These samples work, however your patch would break situations like:
1: 10:int main ()
-: 11:{
-: 12: int i;
-: 13:
22: 14: for (i = 0; i < 10; i++) /* count(11) */
10: 15: noop (); /* count(10) */
where 22 is summed as (1+10+11), which kind of makes sense as it contains
of 3 statements.
Martin
>
>
>> Martin
>>
>>>
>>> Richard.
>>>
>>>
>>>> Hope Nathan will find time to provide review as he's familiar with content
>>>> of gcov.c.
>>>>
>>>> Martin
>>>>
>>>>>
>>>>> OTOH I don't know much about gcov format.
>>>>>
>>>>> Richard.
>>>>>
>>>>>> Martin
>>>>>>
>>>>>>>
>>>>>>> Richard.
>>>>>>>
>>>>>>>> Martin
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Richard.
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>
>>
>
